Control device for controlling a pneumatic piston

ABSTRACT

A control device for controlling a pneumatic piston and cylinder type actuator in conjunction with a 2-position 3-port valve comprises a differential piston mounted in a stepped cylinder bore for sliding movement into one or the other of two end positions according to whether compressed air is admitted under the control of the valve to the smaller diameter end of the bore or to both the smaller and larger diameter ends of the bore. Two ports opening respectively to the smaller and larger parts of the bore are controlled by the differential piston and each acts as a combined flow-and-return passage for pressure fluid for one end of the motor cylinder. A by-pass passage having both ends opening to the larger diameter portion of the bore permits air exhausting from the motor into this portion of the bore, during part of the travel of the differential piston, to by-pass the larger diameter part of the piston and to exhaust to atmosphere via an exhaust port which is in permanently open communication with a part of the bore between the larger and smaller diameter ends of the piston.

United States Patent [1 1 Nussbaumer Dec. 4, 1973 CONTROL DEVICE FOR CONTROLLING A PNEUMATIC PISTON July 13, 1972 [21] Appl. No.: 271,215

[30] Foreign Application Priority Data July 23, 1971 Switzerland 10863/71 [52] US. Cl 91/420, 91/446, 91/461, 137/6256, 137/625.66 [51] Int. Cl. F151) 13/42 [58] Field of Search 137/6256, 625.66, 137/596.14, 596.15, 596.18; 91/420, 461, 304, 446, 468

[56] References Cited UNITED STATES PATENTS 663,727 12/1900 Christie et a1. 137/6256 2,401,258 5/1946 Livers 91/420 X 2,943,604 7/1960 Chubb 1 91/46! X 3,142,315 7/1964 Hennells, Sr 137/6256 Primary Examinerlrwin C. Cohen Attorney-John J. McGlew et a1.

[5 7 ABSTRACT A control device for controlling a pneumatic piston and cylinder type actuator in conjunction with a 2- position 3-port valve comprises a differential piston mounted in a stepped cylinder bore for sliding movement into one or the other of two end positions according to whether compressed air is admitted under the control of the valve to the smaller diameter end of the bore or to both the smaller and larger diameter ends of the bore. Two ports opening respectively to I the smaller and larger parts of the bore are controlled by the differential piston and each acts as a combined flow-and return passage for pressure fluid for one end of the motor cylinder. A.by-pass passage having both ends opening to the larger diameter portion of the bore permits air exhausting from the motor into this portion of the bore, during part of the travel of the differential piston, to by-pass the larger diameter part of the piston and to exhaust to atmosphere via an exhaust port which is in permanently open communication with a part of the bore between the larger'and smaller diameter ends of the piston.

5 Claims, 4 Drawing Figures PAIENIEUDEC 4 ms,

sum 10F 2 Fig.1

PATENTEU DEC 4 SHEET 2 E? 2 I M n M. (xiv/ MP I Fig.3

FIELD AND SUMMARY OF THE INVENTION This invention relates to control devices for actuators operated by pressure fluid, and particularly for pneu matic actuators.

According to this invention there is provided a control device for a pressure fluid operated actuator, which device comprises a casing providing a cylinder bore, and a differential piston which is mounted in the bore for reciprocating movement between two end positions and which has a larger diameter end portion and a smaller diameter end portion. The said cylinder bore has a -smaller diameter portion and a larger diameter portion in which the smaller and larger diameter end portions of the differential piston are respectively slidably disposed for reciprocating movement and which are closed at their ends remote from each other. A

chamber is formed within the bore between the larger and smaller diameter end portions of the differential piston, and the casing provides first and second ports which open tothe ends of the smaller and larger diameter end portions of the bore respectively. A by-pass passage has opposite ends thereof opening to the larger diameter portion of the bore for enabling fluid to by-pass the larger diameter end portion of the differential piston to flow into the chamber over a part of the travel of the differential piston between the end positions. A third port opens to the smaller diameter portion of the bore, which third port communicates with the first port when the differential piston is in one of the two end positions, and communicates with the chamber when the differential piston is in the other of the two end positions. A fourth port opens to the larger diameter portion of the bore which fourth port communicates with the chamber when said differential piston is in the one of its end positions and communicates with the second port when the differential piston is in the other of its end positions, and a fifth port places the chamber in permanently open communication with the ambient atmosphere.

BRIEF DESCRIPTION OF THE- DRAWINGS One embodiment of the invention will now be described by way of example'with reference to the accompanying drawings, in which:

FIG. 1 is a longitudinal section through a control device according to the invention in combination with a 3-port, 2-way valve and a pneumatic actuator, the valve and actuator being shown diagrammatically,

FIG. 2 is a section on line II II of FIG. 1, and

FIGS. 3 and 4 correspond to FIGS. 1 and 2, respectively, show the movable parts in another working position.

DESCRIPTION OF THE PREFERRED EMBODIMENT pipe 5 leading from a compressed-air source. A passage 6 opens to the section 2c at the outerend of the bore, and this passage has a union socket for apipe 7 leading to the 3-port two-way valve 8 which is so connected that the pipe 7 can be connected either with an exhaust orifice 9 or with a pipe 10 leading to thecompressedair source, depending upon the position of the valve. Further transverse bores open to the bore 2 of the casing as follows:

A bore 11 opens to the narrowest portion 2a and is connected by the shortest possible length of connecting pipe 12 to one end of the workingcylinder 13a of a pneumatic actuator 13 and a bore 14 opens to section 2c of the bore 2 and is connected by the shortest possible length of connecting pipe 15 to the other end of the working cylinder 13a in which a piston 13b is displaceable by the compressed air.

Contained in the three-stage bore 2 of the casing l is a differential piston 16, Le. a piston with ends of unequal cross-section, and the piston has an intermediate diameter of which may be 15 mm for example, is indicated at 16a. Two sealing rings 17 and 18 are disposed in grooves in the cylindrical face of this portion 16a of the piston, and a sealing ring 19 is disposed in a groove in the cylindrical face of section 16c. The end closure member 3 has a sealing ring 20, whilst a Seger ring or circlip 22 fitted in a groove 21 holds the end closure member 3 in position.

Opening to section 2b of the bore 2 is a transverse bore 23 which communicates with the atmosphere by way of a noise-inhibiting filter 24. In the section 20 of the bore 2 is a by-pass which is constituted by two transverse bores 25 and 26 which extend from a circular recess 27, closed by a cover-disc 28,- to section 2c of the bore 2, and by an intermediate chamber 29 between the cover-disc 28 and the inner end of the recess 27.

In FIGS. 1 and 2 the various movable parts are shown in the initial position:

The piston 13b of the pneumatic actuator 13 is in its topmost position in the cylinder 13a. Secured directly to this cylinder 13a is the casing of the control element 1 which is connected on the one handy to the compressed-air source through the pipe 5, and on the other to the valve 8 by way of the pipe 7, and this pipe may be relatively long and does not need to be of particularly great cross-section. In the position illustrated, the differential piston 16 of the control device is in the topmost position since the lowest section 2a of the bore 2 is connected to the compressed-air pipe 5, whereas the third section 2c of this bore communiates with the atmosphere by way of the pipe 7. Consequently, the lower zone of the working cylinder 13a is connected to the compressed-air source, so that the piston 13b is held in its uppermost position since the space above the piston 13b communicates with the atmosphere through the pipe 15, the connecting bore 14, the cylindrical space between the intermediate connecting portion 16b of the differential piston 16 and sections 2b and 2c of the bore 2, and the bore 23.

To move the actuator piston 13b to the other end of its stroke, the valve 8 is now actuated so that the pipe 7 and the space above the differential piston 16 in the bore 20 are immediately filled with compressed air. As

soon as the air pressures at the two end faces of the differential piston 16 become equal in magnitude, the piston moves rapidly downwards, since the force acting on the end 16c is greater than that acting on the end 16a. The'differential piston 16 will therefore take up the position illustrated in FIGS. 3 and 4 in which the portion 160 of the piston no longer bears against the end closure member 3, but is located at the lower end .of sec tion 2c of the bore 2, so that on the one hand the passage 6 is connected with the bore 14, and thus the pipe 7, communicating with the pressure source, is connected by way of the pipe to the space above the working piston 13b in the cylinder 13a and, on the other hand the space below the working piston 13b in the cylinder 13a is connected to the atmosphere by way of the pipe 12, the bore 11, theannular chamber surrounding the intermediate portion 16b of the control piston 16, and the bore 23. Thus, the air escaping from the cylinder 130 can do so without restraint, and consequently the working piston 13b can move correspondingly rapidly into the position illustrated in FIGS. 3 and 4.

In this position piston 16 remains under the pressure of the compressed air in the pressure reservoir until the valve 8 is released to enable it to return to the position illustrated in FIG. 1. The result then is that the pipe 7 communicates with the atmosphere through the valve 8 so that the pressure in the pipe 7 and thus the force acting downwardly on the piston 16 become smaller. As soon as the force which acts downwardly on the differential piston 16 becomes smaller than the upwardly acting force, the piston is moved slowly upwards until the portion 16c having the greatest diameter uncovers the bore 26 again. The air in the space above this portion of the piston 16 can now escape to the atmosphere through the transverse bore 25, the chamber 29, the transverse bore 26, the annular chamber surrounding the intermediate portion 16b and through the bore 23 and the noise-inhibiting filter 24, so that the piston 16 rapidly returns to the position illustrated in FIGS. 1 and 2. In this position, the air can escape from the upper portion of the'working cylinder 13a through the pipe 15, the connecting orifice 14, the annular chamber surrounding the intermediate portion 16b and thence through the bore 23 to atmosphere, so that the piston 13b can be rapidly-displaced by the compressed air flowing through the pipe 5, the passage 4, section 2a of the bore 2, the bore 11 and the pipe 12, without the movement being hindered by a delayed discharge of air from the other end of the cylinder 13a.

For reversing a reciprocatable piston in a pneumatic drive unit, use is commonly made of a mechanically actuated S-port 2-position valve by means of which compressed air is applied to one of the two faces of the piston and at the same time the space above the upper face of the piston is connected to the atmosphere to enable the compressed air in this space to escape. Such arrangements are, however, only suitable when the distance between the valve and the drive unit is short. If, however, this distance is great, the slow escape of the air into the atmosphere due to the length of the pipe prevents rapid displacement of the piston, to which compressed air is applied, in the drive unit, since the difference in the pressures on'the two faces of the piston is then too small. For the purpose of overcoming this disadvantage in all those cases in which there is a troublesomely great distance between the actuating or operating member and the pneumatic drive unit, the 5-port 2-way valves are designed as solenoid valves and are fitted directly alongside the drive unit, and there is, so to speak, a completely free choice in the location of the control device However, this carries the not inconsiderable disadvantage that electrical lines are required in addition to the pneumatic ones, so that the assistance of an electrician is necessary in installation, modification and repair operations, and in many instances additional difficulties arise on account of the safetymeasures prescribed, for example, for premises that are damp or where a risk of explosion exists. Therefore, if electrified systems are not used, relatively slowv operation of the pneumatic actuator often has to be accepted. The arrangement described above however provides rapid operation and does not suffer these disadvantages.

In the present arrangement, the control device should be fitted as closely as possible to the reversible actuator, but the 3-port 2-way valve, connected to it through only one pipe, can be disposed at a relatively great distance away without the occurrence of any delay caused by the escape of air to the atmosphere, since the air is discharged directly into the atmosphere from the control element.

I claim: I

1. A control device for a pressure fluid operated actuator, which device comprises a casing providing a cylinder bore, and a differential piston which is mounted in the bore for reciprocating movement between two end positions and which has a larger diameter end portion and a smaller diameter end portion, said cylinder bore having a smaller diameter portion and a larger diameter portion in which the smaller and larger diameter end portions of the differential piston are respectively slidably disposed for said reciprocating movement and which are closed at their ends remote from each other, a chamber being formed within the bore between said larger and smaller diameter end portions of the differential piston, and said casing provid ing first and second ports which open to said ends of the smaller and larger diameter end portions of the bore, respectively, a by-pass passage having opposite ends thereof opening to the larger diameter portion of the bore for enabling fluid to by-pass the larger diameter end portion of said differential piston to flow into the chamber over a part of the travel of said differential piston between said end positions, a third port opening to the smaller diameter portion of the bore which third port communicates with said first port when said differential piston is in one of said two end positions and communicates with the chamber when said differential piston is in the other of said two end positions, a fourth port opening to the larger diameter portion of the bore which fourth port communicates with said chamber when said differential piston is in said one of its end positions and communicates with said second port when said differential piston is in said other of its'end positions, and a fifth port placing said chamber in permanently open communication with the ambient atmosphere.

2. In combination, a pressure-fluid operated actuator comprising a cylinder and a piston slidably mounted in the cylinder, said cylinder having pipe connections at opposite ends thereof, a device for controlling said actuator, which device comprises a casing providing a cylinder bore, and a differential piston which is mounted in the bore for reciprocating movement between two end positions and which has a larger diameter end portion and a smaller diameter end portion, said cylinder bore having a smaller diameter portion and a larger diameter portion in which the smaller and larger diameter end portions of the differential piston are respectively slidably disposed for said reciprocating movement and which are closed at their ends remote from each other, a chamber being formed within the bore between said larger and smaller diameter end portions of the differential piston, and said casing providing first and second ports which open to said ends of the smaller and larger diameter end portions of the bore, respectively, a by-pass passage having opposite I ends thereof opening to the larger diameter portion of the bore for enabling fluid to by-pass the larger diameter end portion of said differential piston to flow into the chamber over a part of the travel of said differential piston between said end positions, a third port which opens to the smaller diameter portion of the bore and which communicates with the first port when the said differential piston is in one of said two end positions, a fourth port which opens to the larger diameter portion of the bore and which communicates with said chamber when said differential piston is in said one of its end positions and with said second port when said differential piston is in said other of its end positions, an exhaust port which is in permanently open communication with said chamber, a first pipe leading from one of said pipe connections of the actuator to said third port, and a second pipe leading from the other said pipe connections of the actuator to said fourth port.

3. In combination, a changeover valve, a control device controlled by the valve, and a pressure-fluidoperated actuator which is controlled by the control device and which comprises a cylinder and a piston slidably mounted in the cylinder, said cylinder having pipe connections at opposite ends thereof; the valve providing a passage communicating with the control device, and an exhaust connection and a supply connection to a source of pressure fluid which connections can selectively be placed in communication with said passage by operation of the valve; said control device comprising a casing providing a cylinder bore, and a differential piston which is mounted in the bore for reciprocating movement between two end positions and which has a larger diameter end portion and a smaller diameter end portion, said cylinder bore having a smaller diameter portion and a larger diameter portion in which the smaller and larger diameter end portions of the differential piston are respectively slidably disposed for said reciprocating movement and which are closed at their ends remote from each other, a chamber being formed within the bore between said larger and smaller diameter end portions of the differential piston, and said casing providing first and second ports which open to said ends of the smaller and larger diameter .end portions of the bore, respectively, a by-pass passage having opposite ends thereof opening to the larger diameter portion of the bore for enabling fluid to bypass the larger diameter end portion of said differential piston to flow into the chamber over a part of the travel of said differential piston between said end positions, said first port being in communication with said source of pressure fluid and said second port communicating with said passage provided by the valve, a third port which opens to the smaller diameter portion of the bore and which communicates with the first port when the said differential piston is in one of said two end positions, a fourth port which opens to the larger diameter portion of the bore and which communicates with said chamber whensaid differential piston is in said one of its end positions and with said second port when said difi'erential piston is in said other of its end positions, an exhaust port which is in permanently open communication with said chamber, a first pipe leading from one of said pipe connections of the actuator to said third port, and a second pipe leading from the other said pipe connections of the actuator to said fourth port. 7

4. A control device for a pressure fluid operated actuator, as claimed in claim .1, in which said chamber is defined by the inner surface of said casing and by a reduced diameter portion of said piston located between said larger and smaller diameter end portions of said piston.

5. A control device for a pressure fluid operated actuator, as claimed in claim 1, including means connecting said first port continuously to a source of fluid under pressure, and means selectively operable to connect said second port to said source or to atmosphere. 

1. A control device for a pressure fluid operated actuator, which device comprises a casing providing a cylinder bore, and a differential piston which is mounted in the bore for reciprocating movement between two end positions and which has a larger diameter end portion and a smaller diameter end portion, said cylinder bore having a smaller diameter portion and a larger diameter portion in which the smaller and larger diameter end portions of the differential piston are respectively slidably disposed for said reciprocating movement and which are closed at their ends remote from each other, a chamber being formed within the bore between said larger and smaller diameter end portions of the differential piston, and said casing providing first and second ports which open to said ends of the smaller and larger diameter end portions of the bore, respectively, a by-pass passage having opposite ends thereof opening to the larger diameter portion of the bore for enabling fluid to by-pass the larger diameter end portion of said differential piston to flow into the chamber over a part of the travel of said differential piston between said end positions, a third port opening to the smaller diameter portion of the bore which third port communicates with said first port when said differential piston is in one of said two end positions and communicates with the chamber when said differential piston is in the other of said two end positions, a fourth port opening to the larger diameter portion of the bore which fourth port communicates with said chamber when said differential piston is in said one of its end positions and communicates with said second port when said differential piston is in said other of its end positions, and a fifth port placing said chamber in permanently open communication with the ambient atmosphere.
 2. In combination, a pressure-fluid operated actuator comprising a cylinder and a piston slidably mounted in the cylinder, said cylinder having pipe connections at opposite ends thereof, a device for controlling said actuator, which device comprises a casing providing a cylinder bore, and a differential piston which is mounted in the bore for reciprocating movement between two end positions and which has a larger diameter end portion and a smaller diameter end portion, said cylinder bore having a smaller diameter portion and a larger diameter portion in which the smaller and larger diameter end portions of the differential piston are respectively slidably disposed for said reciprocating movement and which are closed at their ends remote from each other, a chamber being formed within the bore between said larger and smaller diameter end portions of the differential piston, and said casing providing first and second ports which open to said ends of the smaller and larger diameter end portions of the bore, respectively, a by-pass passage having opposite ends thereof opening to the larger diameter portion of the bore for enabling fluid to by-pass the larger diameter end portion of said differential piston to flow into the chamber over a part of the travel of said differential piston between said end positions, a third port which opens to the smaller diameter portion of the bore and which communicates with the first port when the said differential piston is in one of said two end positions, a fourth port which opens to the larger diameter portion of the bore and which communicates with said chamber when said differential piston is in said one of its end positions and with said second port when said differential piston is in said other of its end positions, an exhaust port which is in permanently open communication with said chamber, a first pipe leading from one of said pipe connections of the actuator to said third port, and a second pipe leading from the other said pipe connections of the actuator to said fourth port.
 3. In combination, a changeover valve, a control device controlled by the valve, and a pressure-fluid-operated actuator which is controlled by the control device and which comprises a cylinder and a piston slidably mounted in the cylinder, said cylinder having pipe connections at opposite ends thereof; the valve providing a passage communicating with the control device, and an exhaust connection and a supply connection to a source of pressure fluid which connections can selectively be placed in communication with said passage by operation of the valve; said control device comprising a casing providing a cylinder bore, and a differential piston which is mounted in the bore for reciprocating movement between two end positions and which has a larger diameter end portion and a smaller diameter end portion, said cylinder bore having a smaller diameter portion and a larger diameter portion in which the smaller and larger diameter end portions of the differential piston are respectively slidably disposed for said reciprocating movement and which are closed at their ends remote from each other, a chamber being formed within the bore between said larger and smaller diameter end portions of the differential piston, and said casing providing first and second ports which open to said ends of the smaller and larger diameter end portions of the bore, respectively, a by-pass passage having opposite ends thereof opening to the larger diameter portion of the bore for enabling fluid to by-pass the larger diameter end portion of said differential piston to flow into the chamber over a part of the travel of said differential piston between said end positions, said first port being in communication with said source of pressure fluid and said second port communicating with said passage provided by the valve, a third port which opens to the smaller diameter portion of the bore and which communicates with the first port when the said differential piston is in one of said two end positions, a fourth port which opens to the larger diameter portion of the bore and which communicates with said chamber when said differential piston is in said one of its end positions and with said second port when said differential piston is in said other of its end positions, an exhaust port which is in permanently open communication with said chamber, a first pipe leading from one of said pipe connections of the actuator to said third port, and a second pipe leading from the other said pipe connections of the actuator to said fourth port.
 4. A control device for a pressure fluid operated actuator, as claimed in claim 1, in which said chamber is defined by the inner surface of said casing and by a reduced diameter portion of said piston located between said larger and smaller diameteR end portions of said piston.
 5. A control device for a pressure fluid operated actuator, as claimed in claim 1, including means connecting said first port continuously to a source of fluid under pressure, and means selectively operable to connect said second port to said source or to atmosphere. 